1. Field of the Invention
The present invention relates to a process and an apparatus for nickel plating of an object such as electronic parts as well as a nickel-plated product produced by the apparatus according to the process. Particularly, the present invention relates to a technique for electrolessly plating a Nixe2x80x94B layer on the surface of a substrate and then a Nixe2x80x94P layer thereon.
2. Description of the Prior Art
One example of such nickel plating processes is disclosed in Japanese Patent Application Laid-Open No. 8-281957. This process involves laminating electrolessly deposited Nixe2x80x94B and Nixe2x80x94P layers, thereby intending to provide a nickel film which is free of membrane stress.
In this process, a pattern is formed on a ceramic substrate which is then subjected to a pretreatment by sensitizing-activation process. Next, a mask such as a resist may be stripped from the substrate which is then subjected to electroless Nixe2x80x94P plating. The plating solution may comprises nickel salt (0.05-0.15 mo/l), a complexing agent, tartrate or glycin (0.075-0.225 mol/l), and a reducing agent, dimethylamine borane (0.5-4 g/l). The Nixe2x80x94B plating solution further contains sodium hydrate for adjusting the pH condition of the solution within the range of 5.0-7.0. The ceramic substrate is immersed the Nixe2x80x94B plating solution which has been heated to 50xc2x0 C. for 20 minutes for plating
Thereafter, the plated substrate is washed with pure water and subjected to electroless Nixe2x80x94P plating. The Nixe2x80x94P plating solution comprises nickel salt (0.05-0.15 mo/l), a completing agent, tartrate or glycin (0.075-0.225 mol/l), and a reducing agent, sodium hypophosphite (10-30 g/l). The Nixe2x80x94P plating solution further contains sodium hydrate for adjusting the pH condition of the solution within the range of 5.0-7.0. The ceramic substrate is immersed in the Nixe2x80x94P plating solution has been heated to 50xc2x0 C. for 50 minutes to obtain a nickel layer having a thickness of about 2 xcexcm formed on the substrate.
These conventional electroless plating processes, however, often resulted in a ceramic substrate having a thinner portions present in some areas where Nixe2x80x94P has not been deposited, particularly when the substrate to be plated has a large surface or when a large number of substrates are plated at one time. This thin portions may cause quality variations among the resulting products and thus cannot provide unstressing effect as described in the Japanese Patent Application Laid-Open No. 8-281957, just partially improvement of corrosion resistance by Nixe2x80x94P layer.
One object of the present invention is to provide a process for nickel plating which comprises the steps of electrolessly forming a Nixe2x80x94B layer on a substrate and then a uniform and even Nixe2x80x94P layer on the Nixe2x80x94B layer.
Another object of the present invention is to maintain the concentration of the Nixe2x80x94B plating solution deposited on the substrate in the above-described process.
These and further objects of the present invention are achieved by the novel process and apparatus for nickel-plating as well as nickel-plated product of the present invention.
One aspect of the present invention provides a nickel plating process which comprises the steps of: electrolessly plating a Nixe2x80x94B layer on a substrate and then a Nixe2x80x94P layer on the Nixe2x80x94B plated substrate to obtain a substrate having a Nixe2x80x94B layer formed on the surface thereof and a Nixe2x80x94P layer superimposed on the Nixe2x80x94B layer formed on the substrate. In this process, the substrate is subjected to drying-protection treatment after the Nixe2x80x94B plating step and before the Nixe2x80x94P plating step. In this way, a uniform and even Nixe2x80x94P layer can be electrolessly plated on the electrolessly deposited Nixe2x80x94B layer.
Another aspect of the present invention provides a nickel plating apparatus which comprises: a Nixe2x80x94B plating bath containing a Nixe2x80x94B plating solution in which a substrate is immersed for electroless Nixe2x80x94B deposition; a Nixe2x80x94P plating bath containing a Nixe2x80x94P plating solution in which the substrate having the Nixe2x80x94B layer formed thereon is immersed for electroless Nixe2x80x94P deposition; and a transporting member for transporting the substrate from the Nixe2x80x94B plating bath to the Nixe2x80x94P plating bath; wherein the Nixe2x80x94B layer formed on the substrate is prevented from drying during the transportation of the substrate from the Nixe2x80x94B plating bath to the Nixe2x80x94P plating bath. In this way, a uniform and even Nixe2x80x94P layer can be electrolessly plated on the electrolessly deposited Nixe2x80x94B layer.
Another aspect of the present invention provides a nickel plated product produced in the nickel plating apparatus according to the nickel plating process of the present invention. The nickel placed product comprises: a surface; a Nixe2x80x94B layer which is electrolessly plated on the surface; and a Nixe2x80x94P layer having substantially uniform thickness which is electrolessly plated on the entire surface of the Nixe2x80x94B layer. Accordingly, a nickel plated product which has a Nixe2x80x94B layer and a substantially uniform Nixe2x80x94P layer electrolessly formed thereon can be obtained by using the nickel plating apparatus and/or process of the present invention.